1. Field of the Invention
The present invention relates to a semiconductor device comprising thin film semiconductor layers such as a solar battery and a method of manufacturing the same. Specifically, it relates to a semiconductor device manufactured through forming thin film semiconductor layers on a provisional substrate and then transcribing it on another substrate, and a method of manufacturing the same.
2. Description of the Related Art
In recent years, solar batteries have come to be in practical use. It is necessary to save resources and to decrease costs to utilize solar batteries in full-scale. Thin film solar batteries are preferred to thick film solar batteries when energy conversion (light-electricity) efficiency and shortening the cycle of energy recycle are taken into consideration.
The same applicants as this application have first proposed a method of separating an element formation layer from a substrate (Japanese Patent Application laid-open Hei 8-213645). In the method, a porous layer is formed on a single crystalline substrate as an isolation layer and a semiconductor layer to be a solar battery is grown on the porous layer. Then, a plastic plate or a glass plate is adhered onto the semiconductor layer using an adhesive, and the semiconductor layer is exfoliated from the single crystal substrate together with the plastic plate or the glass plate by applying tensile stress.
As described, a thin film solar battery of the related art is manufactured by transcribing it onto a plastic plate or a glass plate. As a result, warp is generated because of the difference in thermal expansion of the solar battery and the plastic plate, resulting in the destruction of the solar battery. Also, a glass plate is difficult to be applied depending on its usage since it is hard to be folded or to be cut.
Furthermore, as the plastic plate and the glass plate are not spontaneously decomposed, the solar battery which becomes unusable must be artificially decomposed when being disposed. Therefore, there is a problem of waste disposal such as running cost of decomposing, if solar batteries becomes widespread use in full-scale, and if there are a large amount of the solar batteries which are unusable.
The invention has been designed to overcome the forgoing problems. The object is to provide a semiconductor device in which warp is suppressed and processing and disposing can be easily performed, and a method of manufacturing the same.
A semiconductor device of the invention comprises: thin film semiconductor layers having one side and the other side facing each other; and a first substrate made of a material including cellulose which is positioned on the one side.
A method of manufacturing a semiconductor device of the invention includes the steps of: depositing thin film semiconductor layers on a provisional substrate; exfoliating the thin film semiconductor layers from the provisional substrate; and transcribing the thin film semiconductor layers onto the first substrate.
In the semiconductor device of the invention, the first substrate is formed of a material containing cellulose. Therefore, the difference in thermal expansion of the first substrate and the thin film semiconductor layers is decreased and warp caused by changes in temperature is suppressed. Also, the semiconductor device becomes light and processing becomes easy. Furthermore, the thin film semiconductor layer can be spontaneously decomposed so that disposal becomes easy.
In the method of manufacturing a semiconductor device of the invention, after thin film semiconductor layers are deposited on a provisional substrate, the thin film semiconductor layers are exfoliated from the provisional substrate; and the thin film semiconductor layers are transcribed onto the first substrate.
Other and further objects, features and advantages of the invention will appear more fully from the following descriptions.